Other mistake: Before the battle, the leader of the waterbenders says that he will have everyone extinguish as many sources of fire as possible. When the firebenders come up from the ground at the start of the battle, all of the torches lighting the city are lit.
Other mistake: In a hockey game, Derek Thompson slams an opposing player into the wall and knocks out a tooth. Inexplicably, the tooth shoots straight up into the air and there is absolutely no blood on the tooth or around the player's mouth.
Other mistake: When the ride finishes, there is no sign of a safety bar in Gru's cart.
Other mistake: Flynn and Rapunzel go through the Snugly Duckling tunnel. Later when Maximus points to it, you could easily see it from anywhere in the pub. But nobody saw Flynn and Rapunzel go through other than the thug who showed them.
Other mistake: When Tamina pretends to have fainted and Dastan runs over to her rescue, Dastan wearing some kind of Adidas/Nike/other modern sport shoes, only the shoe sole is visible but you can see it as he runs and kneels just before he gets whacked on the head. (00:36:45)
Other mistake: Eustace's diary seems to be perfectly fine as he was making entries on board the ship despite it being fully exposed to the sea water.
Other mistake: In the last scene when Jeep, Charlie, and the baby are driving off, the gearshift of the truck is located in "park". That is located at the topmost point of the gearshift's travel.
Other mistake: Harry pulls a knife out of Dobby's chest, but before that, we can see there's no knife.
Suggested correction: Yes there is, Dobby is holding on to it as he falls into Harry's hands. Its not totally obvious, but the CGI people definitely put it in.